Puppet masters

Earlier this year Facebook revealed that about 5-6% of its 901 million users might be fake - representing up to 54 million profiles.

Graham Cluley of the security firm Sophos said this was a major problem.

"Spammers and malware authors can mass-produce false Facebook profiles to help them spread dangerous links and spam, and trick people into befriending them," he said.

"We know some of these accounts are run by computer software with one person puppeteering thousands of profiles from a single desk handing out commands such as: 'like' as many pages as you can to create a large community.

"I'm sure Facebook is trying to shut these down but it can be difficult to distinguish fake accounts from real ones."

A spokesman for the social network said: "We don't see evidence of a 'wave of likes' coming from fake users or 'obsessive clickers'."

But Mr Cluley said it was in the firm's interest to downplay the problem.

"They're making money every time a business's advert leads to a phoney Facebook fan," he said.

'Suspicious' fans

Michael Tinmouth, a social media marketing consultant, ran Facebook advertising campaigns for a number of small businesses, including a luxury goods firm and an executive coach.

At first, his clients were pleased with the results. But they became concerned after looking at who had clicked on the adverts.

While they had been targeting Facebook users around the world, all their "likes" appeared to be coming from countries such as the Philippines and Egypt.

"They were 13 to 17 years old, the profile names were highly suspicious, and when we dug deeper a number of these profiles were liking 3,000, 4,000, even 5,000 pages," he said.

Mr Tinmouth pointed out a number of profiles which had names and details that appeared to be made up.